Method of anisotropic etching of silicon

Abstract

A method of anisotropic etching of silicon with structures, preferably defined with an etching mask, by using a plasma, with a polymer being applied during a polymerization step to the lateral border of the structures defined by the etching mask, then being partially removed again during the following etching step and being redeposited in deeper side walls of the structure newly formed due to the etching reaction, and the etching is performed with an etching gas containing 3 to 40 vol % oxygen. In this way it is possible to prevent sulfur contamination in the exhaust gas area in high rate etching of silicon.

What is claimed is:  
     
       1. A method of anisotropic etching of silicon with structures by using a plasma, comprising the steps of: 
       a) applying a polymer, using a polymerization process and an oxygen-free passivation gas, to a lateral border of the structures;  
       b) simultaneously:  
       partially removing the applied polymer using an etching process, the etching process being performed with an etching gas containing sulfur, fluorine, and 3 to 40 vol % oxygen, and  
       redepositing the polymer in deeper portions of a side wall newly formed by the etching process, wherein:  
       a performance of the polymerization process is alternated with a performance of the etching process; and  
       c) oxidizing sulfur atoms in an area of a vacuum pump and in an exhaust gas line, wherein the oxidation of the sulfur atoms prevents an interfering deposition of sulfur in the pump and in the exhaust gas line.  
     
     
       2. The method according to  claim 1 , wherein the structures are defined by an etching mask. 
     
     
       3. The method according to  claim 1 , wherein the etching gas contains 5 to 25 vol % oxygen during an entire duration of the etching process. 
     
     
       4. The method according to  claim 1 , wherein the etching gas contains 10 to 15 vol % oxygen during an entire duration of the etching process. 
     
     
       5. The method according to  claim 1 , wherein the etching gas is used only during intervals of 0.1 to 1 second within the etching process. 
     
     
       6. The method according to  claim 1 , wherein a media used in the etching process and the polymerization process has gas flow rates of 10 to 200 cm 3  [STP]/min and process pressures of 5 to 100 μbar. 
     
     
       7. The method according to  claim 1 , further comprising the step of generating a plasma with a microwave radiation at powers between 100 and 1500 W. 
     
     
       8. The method according to  claim 1 , further comprising the step of generating a plasma with a microwave radiation at a power between 100 and 2000 W with an inductive excitation. 
     
     
       9. The method according to  claim 1 , further comprising the step of applying power to a substrate electrode to accelerate ions to the substrate. 
     
     
       10. The method according to  claim 1 , wherein the etching gas contains 20 to 40 vol % oxygen during an entire duration of the etching process. 
     
     
       11. The method according to  claim 1 , wherein the etching gas contains only a compound of sulfur and fluorine and 3 to 40 vol % oxygen. 
     
     
       12. The method according to  claim 1 , wherein the etching process includes the step of exposing substrates to an ion energy of 1 to 50 eV during an entire duration of the etching process. 
     
     
       13. The method according to  claim 12 , wherein the ion energy is 5 to 30 eV. 
     
     
       14. The method according to  claim 1 , wherein the polymerization process includes the step of exposing substrates to an ion energy of 1 to 50 eV. 
     
     
       15. The method according to  claim 14 , wherein the ion energy is 5 to 30 eV. 
     
     
       16. The method according to  claim 14 , wherein the ion energy is 15 eV. 
     
     
       17. A method of anisotropic etching of silicon with structures by using a plasma, comprising the steps of: 
       a) applying a polymer, using a polymerization process and an oxygen-free passivation gas, to a lateral border of the structures;  
       b) simultaneously:  
       partially removing the applied polymer using an etching process, the etching process being performed with an etching gas containing sulfur, fluorine, and 3to 40 vol % oxygen, the oxygen being used only at a beginning of the etching process and  
       redepositing the polymer in deeper portions of a side wall newly formed by the etching process, wherein:  
       a performance of the polymerization process is alternated with a performance of the etching process; and  
       c) oxidizing sulfur atoms in an area of a vacuum pump and in an exhaust gas line, wherein the oxidation of the sulfur atoms prevents an interfering deposition of sulfur in the pump and in the exhaust gas line.  
     
     
       18. A method of anisotropic etching of silicon with structures by using a plasma, comprising the steps of: 
       a) applying a polymer, using a polymerization process and an oxygen-free passivation gas, to a lateral border of the structures;  
       b) simultaneously:  
       partially removing the applied polymer using an etching process, the etching process being performed with an etching gas containing sulfur, fluorine, and 3 to 40 vol % oxygen, the oxygen being used only at an end of the etching process, and  
       redepositing the polymer in deeper portions of a side wall newly formed by the etching process, wherein:  
       a performance of the polymerization process is alternated with a performance of the etching process; and  
       c) oxidizing sulfur atoms in an area of a vacuum pump and in an exhaust gas line, wherein the oxidation of the sulfur atoms prevents an interfering deposition of sulfur in the pump and in the exhaust gas line.